Control switch for microwave oven

ABSTRACT

The switch structure disclosed coordinates the position of two plunger members, one manually actuated and one engaged by an oven door, so that a switch operated member is incrementally moved into switch-closing position by sequential depression of the two plunger members. Both plunger members must be actuated before the switch member can reach its switch closing position.

United States Patent Ball.

[54] CONTROL SWITCH FOR MICROWAVE OVEN [72] Inventor: Wesley L. Ball,Marion, Ind.

, [73] Assignee: Appliance Manufacturing Company,

Inc., Van Buren, Ind.

[22] Filed: Oct. 4, 1971 [211 App]. No.: 186,332

[52] US. Cl. ..200/50 A, 219/1055 [51] ..H01h 9/22 [58] Field of Search..200/50 A, 50 C, 61.62;

[56] References Cited UNITED STATES PATENTS 3,504,144 3/1970 Horner..200/61.62

[ 51 Sept. 12,1972

3,560,677 2/1971 Mequon ..200/50 C Primary Examiner-Robert K. SchaeferAssistant Examiner-M. Ginsburg Attorney-Maurice A. Weikart [5 7]ABSTRACT The switch structure disclosed coordinates the position of twoplunger members, one manually actuated and one engaged by an oven door,so that a switch operated member is incrementally moved intoswitchclosing position by sequential depression of the two plungermembers. Both plunger members must be actuated before the switch membercan reach its switch closing position.

7 Claims, 7 Drawing Figures P'ATENTEDSEP 12 I972 sum 1 or 2 INVENTORWESLEY L. BALL ATTORNEYS PATENTEDSEP 12 1912 3.691, 329

SHEET20F2 Fig FigT.

INVENTOR WESLEY L. BALL m 2 KM n mimhauHiWBn ATTORNEYS 1 CONTROL SWITCHFOR MICROWAVE OVEN BACKGROUND OF THE INVENTION Microwave ovens have comeinto increasing use, and such ovens, particularly domestic microwaveovens used for rapid cooking of food, have an imperative requirementthat access to the interior of the oven can only be had when themicrowave generating element is deenergized. Provision of a push-buttonon-off switch controlling the element is, along, not sufficient. Use ofv an oven door actuated switch, uncoordinated with any other control, isalso insufficient in itself to remedy the safety hazard inherent inutilization of microwave ovens. A relatively simple, fail-safe controlwhich coordinates the position of the oven door with a manually operablemember to assure that oven interior access is denied unless themicrowave generating element is deenergized is, therefore, a necessarycomponent of a safe, commercially successful microwave food cookingoven.

The concept of the present invention provides a control switch assemblyfulfilling these requirements in which the opening and closing of themicrowave element controlling switch is not dependent upon springloading but is, instead positively and mechanically actuated by motionof a pair of plunger elements, moved in proper sequence by a manualpush-button and by the oven door.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top plan view of a switchassembly embodying the present invention, with portions of the housingbroken away.

FIG. 2 is a sectional side view taken generally along the line 2-2 ofFIG. 1.

FIG. 3 is a front view of the switch assembly shown in FIGS. 1 and 2.

FIG. 4 is a top plan view of the door actuated component of the switchassembly.

FIG. 5 is a side sectional view, similar to FIG. 2 but taken generallyat the centerline (parallel with and viewing in the same direction asline 2-2 of FIG. 1) and showing the switch assembly in the positionassumed when the oven door is closed but prior to actuation of themanual control.

FIG. 6 is a view similar to FIG. 5 but showing the switch assembly inthe position assumed when the oven door has been closed and the manualcontrol has been actuated.

FIG. 7 is a side sectional view of a modified form of the switchstructure shown in FIGS. 1-6.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring initially to FIGS. 1and 2, the switch assembly embodying the present invention includes ahousing having a top wall 10, a front wall 11, a rear wall 12, sidewallsl3 and 14 and a base 16 (FIG. 2). Mounted on the exterior face of thetop wall is a solenoid 17 whose plunger is rigidly secured to a member18 (FIG. 2) which extends within the housing and is moved upwardly bythe solenoid plunger when the solenoid is energized for a purpose to besubsequently explained.

Mounted on terminals 19 and 21 which extend into the interior of thehousing are fixed or stationary electrical contacts 19a and 21a. Amovable contact member 22, carrying movable electrical contacts 23 and24 is positioned adjacent opposite the fixed contacts, the contacts 23and 24 being adapted to engage and thus electrically bridge the fixedcontacts 19a and 21a when the movable contact member 22 is placed inclosed position. The bridging of contacts 19a and 21a closes theelectrical circuit between the terminals 19 and 21 and, it will beunderstood, controls the energized and deenergized condition of themicrowave radiating element (not shown) which is operated by the circuitthrough terminals 19 and 21.

As may best be seen in FIG. 2, the contact carrying member 22 isresiliently supported, by means of spring 26, on an electricallynon-conducting plunger-bridging member 27, the member 27 having acentrally extending portion 27a against which the spring 26 bottoms. Theends of the member 27 are rounded, as indicated in FIG. 2, and extendinto apertures in spaced plunger members, identified at 28 (FIG. 5) and29 (FIG. 2), the member 27 thus extending between the plunger members 28and 29 and being pivotally attached thereto. As will be evident fromFIG. 1 and 5, a sidewardly extending portion 280 of the plunger member28 carries the aperture through which the rounded upper end of themember 27 extends. As will be evident from FIG. 4, the aperture 29b,into which lower rounded end of the member 27 extends, is carried by anauxiliary leg 29a which is integral with and extends parallel to themain body of the plunger 29. As will be evident from FIGS. 1

and 2, an additional plunger member 31, acting as a stop plunger extendsacross the housing and is parallel with and aligned with the plunger 28.The stop plunger 31, although extending parallel to plunger 28, islaterally spaced from it and is not connected to the plunger bridgingmember 27.

- All three of the plunger members 28, 29 and 31 are supported in thehousing so as to permit limited axial motion of the plungers.Compression spring 32 carried on the plunger 29, compression spring 33carried on the plunger 31, and compression spring 34 (FIG. 5), carriedon the plunger 28, serve as resilient means biasing or urging therespective plungers to the limit of their leftward (as viewed in thedrawings) position in the housing.

As many best be seen in FIGS. 1 and 3, the plungers 28 and 31 areadditionally bridged, exteriorly of the housing, by an interlock meanstaking the form of a member 36 whose ends extend freely throughapertures in the portions of the plungers 28 and 31 just exterior of thehousing front wall 11. The member 36 extends into a slot 38 in the wall11, and as may best be seen in FIG. 3, the slot 38 is discontinuous andthe portion 39 of the wall 11 provides a-bearing against which thecentral portion of the member 36 bears to provide a central fulcrum forthe member 36 permitting it to move angularly as one or the other of theplungers 28 or 31 is manually actuated, the interlock assuring that bothplungers cannot be in depressed, or actuated position simultaneously. Itwill be understood that the outer ends of the plungers 28 and 31 bothcarry push-buttons, these push-buttons being shown in phantom lines inFIGS. 2, 5 and 6, together with surrounding portions of the oven controlpanel and wall, none of which form specific elements of the presentinvention.

As will be evident particularly from FIGS. 2, 5 and 6, the door engagedplunger member 29, capable of axial movement within the housing, is alsomounted for controlled pivotal motion, the pivotal motion occurringgenerally about the junction of the member 29 with the housing rear wall12 as a fulcrum. As may best be seen in FIG. 4, the member 29 isapertured as indicated at 290 for accommodating the tip 41a (FIG. 2) ofa retaining member 41 whose function and configuration will besubsequently described. Referring again to FIG. 4, a generally U-shapedcut-out portion in the member 29 defines an upturned tongue or abutment29d which, as may be seen in FIG. 2, is adapted to be engaged by a latchmember 42 carried by the oven door 43, engagement of the door abutment42 with the portion 29d of the plunger occurring as the door is movedinto closed position. As may best be seen in FIGS. 2 and 4, a portion ofthe member 29, identified as 29c, is bent upwardly and this upwardlybent portion is provided with sidewardly extending tabs 29f and adownwardly turned latch or hook portion identified at 29g.

As will be evident from FIGS. 2 and 3, the front wall 11 of the housingis provided with a generally rectangular aperture 44, the portions ofthe housing wall removed to provide the aperture being bent rearwardlyto the interior of the housing to form inwardly extending, rectangularflanges 46. These flanges are provided with diagonally directed, orinclined slots 47 which accommodate the tabs 29f on the plunger 29 andalong which the tabs ride as the plunger is moved axially within thehousing thus providing the controlled pivotal movement of the plunger 29previously referred to.

A comparison of FIGS. 2 and 5 will make evident that the retainingmember 41, previously mentioned, extends generally vertically within thehousing and is composed of a transverse portion 41f which extendsbetween two identical, rearwardly extending, triangularly-shaped flanges41b and 41c. The reduced ends of the flanges extend through slots in thetop wall as will be evident from FIG. 1. Inside the housing, the reducedupper ends of the flanges 41b and 41c accommodate compression springs41d (FIG. 2) and 41e (FIG. 5) which serve to resiliently bias or urgethe retaining member 41 generally, axially downward in the housing. Thetip portion 41a of the member 41 is of reduced width and, as mentionedwith reference to FIG. 4, extends into the aperture 29c in the member29. As will be evident from FIGS. 2 and 5, the lower housing wall 16 isprovided with a tab 51 which is struck from the housing wall and acts asa locking abutment and is adapted to engage the extending tip 41a of themember 41 during operation of the switch structure as will subsequentlybe described. As may best be seen in FIGS. 5 and 6, the member 41 isfurther provided with an additional transverse bar 52 which is adaptedto be engaged by the notch 28b and the inclined surface 28con the uppermargin of plunger 28. As may best be seen in FIG. 2, the transverse bar52 is also adapted to be engaged by the member 18 moved by the plungerof the solenoid 17.

In operation, referring initially to FIG. 2, the switch assembly isshown in the position assumed by the plungers when the oven door 43 isopen and neither of the manually actuated plunger members 28 and 31 aredepressed or actuated. Under these conditions and the contacts 23-24 areseparated from the contacts 19a21 so that the electrical circuit betweenthe terminals l9 and 21 is open. The portion 29e of the plunger 29 is inthe upward extreme of the pivotal movement of the member 29 and theplunger is in its extreme leftward position because of the force exertedby the compression spring 32. The plungers 28 and 31 are also in theirextreme leftward position, the retaining member 41 is also in its upperposition, being held there by its engagement with the member 29, thesprings 41d and 41e being compressed. The member 18 operated by thesolenoid 17, although in engagement with the bar 52 of the member 41,exerts no upward force on it since solenoid 17 is deenergized. Theinclined surface 31a (FIG. 2) on the upper margin of the plunger 31 isout of engagement with the transverse bar portion 52 of the member 41and the inclined surface 28c and notch 28b (FIG. 5) on the upper marginof the plunger 28 are also separated from the transverse portion 52 ofthe member 41. Referring to FIG. 5, when the oven door 43 is closed asthere indicated, the portion 42 of the oven door engages the portion 29dof the plunger 29 and moves it axially rightwardly as viewed in FIG. 5compressing somewhat the spring 32. This rightward motion of the plunger29 cocks or tilts the member 27 to its position of FIG. 5 thereby movingthe contacts 23 and 24 incrementally toward the fixed contact and 21a,respectively. This rightward motion of the plunger 29 further causes thetabs 29f to ride downwardly within the slots 47 to thereby pivotallymove the member 29 downwardly so that the extending end 29g of themember closes over the portion 42 of the door to latch the door toclosed position.As this rightward motion of the member 29 takes place,the springs 41d and 41e will cause the lower end of the member 41 tofollow the member 29 thereby lowering the member 41 within the housinguntil the transverse portion 52 engages the upper edge of the plunger28, the position shown in FIG. 5. It will be noted from FIG. 5 that withthe door closed, but prior to the depression of the plunger 28 manuallythe switch contacts 19a-21 remain open, that is, unbridged by contacts23-24.

Referring to FIG. 6, the switch components are shown in the positionassumed when the plunger 28 is depressed manually, by means of itspush-button, with the oven door 43 closed. Under these conditions, therightward movement of the plunger 28 will move the upper end of themember 27 to its position of FIG. 6, thereby providing the finalincrement of motion for the member 27 necessary to move the contactsinto closed position and completing the electrical circuit between theterminals 21 and 19 permitting the microwave element to be energized.This rightward movement of the plunger 28 permits the transverse portion52 of the member 41 to move along the inclined surface 280 of the member28 and into the notch 28b as shown in FIG. 6. The resulting slightdownward motion of the member 41, under the bias of springs 41d and4'le, causes the tip portion 41a of the member 41 to engage the end ofand be positively locked by, the locking abutment 51. Under theseconditions the oven door 43 is locked closed, the plunger 28 is held inits rightward position so that the contacts are held closed, andoperation of the oven may proceed. It should be noted that theincremental movement of the member 27 into contactsclosing position,shown in FIG. 6, occurs because of the sequential, mechanically producedrightward motion of the plunger 29 and the plunger 28 and this closingmotion is not dependent of spring action. The locking abutment 51provides a rigid mechanical lock preventing leftward motion of theplunger 29 thereby preventing a forced opening of the oven door 43 aslong as member 41 is in its position of FIG. 6.

Except as a result of energization of'solenoids 17, to be subsequentlydescribed, the oven door cannot be reopened unless the stop plunger 31(FIG. 2) is depressed, that is, moved axially rightwardly by manuallyactuating its push-button. When this occurs, the inclined surface 31a(FIG. 2) on the plunger 31 engages the underside of the transverseportion 52 of the member 41 and cams it upwardly. Simultaneously, the

interlock member 36 (FIGS. 1 and 2) is angularly moved counterclockwise(as viewed in FIG. 1) to force the plunger 28 outwardly into itsde-actuted position, the transverse portion 52 having been lifted out ofthe notch 28b by the caming action of the inclined surface 31a on theplunger 31. This lifting of the member 41 also withdraws the tip 41afrom engagement with the locking abutment 51 so that the door 43 canthen be opened. This motion of the plunger 28 and 29 also, of course,disengages the switching contacts and the switch components assume theirpositions of FIG. 2.

It will be understood that the above described procedure for opening theoven door and deenergizing the radiating element may be utilizedwhenever the oven door has been closed. However, in the normal course ofevents, during a normal baking cycle, for example, the time during whichthe oven is to be energized will be controlled by a timer (not shown)which at the end of the selected time period will provide an electricalimpulse momentarily energizing the solenoid 17 indicating the end of thecooking period. When the solenoid 17 is momentarily energized, itplunger will raise the member 18 (FIG. 2) applying a lifting force tothe underside of the transverse portion 52 of the member 41. Thisresults in an upward motion of the member 41, lifting the member 52 outof the notch 28b in the plunger 28, and permitting the spring 34 todrive the plunger 28 leftwardly (as viewed in FIG. 5) to thereby openthe switch contacts and release the oven door for opening as previouslydescribed.

A modified and simplified version of the switch assembly is illustratedin FIG. 7. As there shown, a start plunger 61 (comparable to plunger 28)extends across the housing 62. A stop plunger (comparable to plunger 31)also extends across the housing adjacent the plunger 61 but is not shownin FIG. 7. This stop plunger is interlocked with the start plunger 61 bymeans of the interlock member 63 (comparable to the interlock member36). The stop plunger (not shown) has no function other than to providea means for driving the start plunger leftwardly or outwardly (as viewedin FIG. 7) when the stop plunger is actuated, and to raise the member71. Extending between the plunger 61 and a door plunger 64 is a plungerbridging member 66 (comparable to the member 27 previously mentioned)which carries movable contacts 67 adapted to engage fixed contacts 68.The door plunger 64, at its end 64a, exterior of the housing, is adaptedto be engaged by the oven door as it is closed the plunger 64 beingthereby depressed or moved rightwardly, as viewed in FIG. 7, thismovement of the plunger 64 being resisted by the compression spring 69.A retaining member 71 extends generally vertically within the housingand is comparable to the retaining member 41 in the structure of FIGS.1-6. The member 71 is provided with a tab or abutment 71a which isadapted to ride the inclined surface 61a on the plunger 61 and to dropinto the notch 61b on the plunger 61 when these elements are inappropriate position. A central shoulder 71b on the member 71 restsagainst the upper margin of the plunger 64, the inclined or rampsurfaces 64b and 64c on the upper margin of the plunger 64 being adaptedto be engaged by the shoulder 71b under various operating conditions ofthe assembly. A compression spring 72 functions to bias or urge themember 71 downwardly, as viewed in FIG. 7. A compression springfunctions to bias the plunger 61 outwardly or leftwardly, as viewed inFIG. 7.

In operation, with the switch assembly components in their positions ofFIG. 7, the switch contacts 67 and 68 are open. When the oven door isclosed, as the door engages the tip 640 of the plunger 64, the plungerwill be moved rightwardly, as viewed in FIG. 7, and this incrementallymoves the contacts 67 toward the contacts 68 but such motion, alone, isnot enough to close the contacts. The shoulder 71b on the member 71rides down the ramp 64b and the spring 72 moves the abutments 71a on themember 71 down into engagement with the inclined surface 61a on theplunger 61. With the oven door closed and the contacts 67 movedpartially toward closed position, the push-button tip of the plunger 61maybe manually actuated, compressing the spring 70 and moving the notch61b beneath the abutment 71a lowering the member 71 into the notch. Withthis rightward movement of the plunger 61 the final increment of motionof the contacts 67, necessary to close them against contacts 68, will beimparted to the member 66 and the circuit through the switch assemblywill be closed to energize the microwave radiating element (not shown).

After the switch contacts have been closed, they may be reopened eitherby opening the oven door, releasing the plunger member 64, or bydepressing the stop button to lift member 71 and angularly move theinterlock member 63 to thereby drive the plunger 61 leftwardly, asviewed in FIG. 7, into its de-actuated position. If the contacts areopened by the opening of the oven door, it will be evident that theleftward movement of the plunger 64 will cause the ramp 64b to lift, ormove upwardly, the member 71 releasing the plunger 61 to move to itsleftward, de-actuated position. The leftward movement of the plunger 64and of the plunger 61 will, of course, place the member 66 in itsposition of FIG. 7 in which the contacts 67 and 68 are opened. When thestop button is pushed while leaving the oven door closed the leftwardmovement of the member 61 will cause the contacts 67 and 68 to open. Therightward movement of the stop plunger (not shown) causes an inclinedportion of that plunger to engage the abutment 71a on the member 71 tolift member 71 permitting release of the member 61 for its movementleftwardly.

From the foregoing it should be noted that in the switch assembliesdescribed, depressing or actuating either the start plunger or the ovendoor engaged plunger will not alone be sufficient to close the switchcontacts. Closure of the switch contacts requires that both plungers beactuated and the door engaged plunger must be depressed or actuatedfirst otherwise the start plunger will not be held in its actuatedposition but will return to de-actuated position when fingerprcssurcunlncslannullonlsmleaiefl.lnmeilruelure described with referenceto FIG. 7,.the oven door is not latched closed but may be opened,however, this opening of the oven door will open the switch contacts. Inthe structure described with reference to FIGS. l6 the oven door 43 islatched closed and cannot be opened until the stop button is depressedor until the solenoid 17 is momentarily energized. In the opening of thecontacts, either by means of the door plunger 29 or the start plunger28, the opening movement is mechanically produced so that the movableand fixed contacts are mechanically opened and the opening force on thecontacts is not dependent on return spring bias which might fail to openthe contacts should they be welded or otherwise abnormally stick closed.The positive lock provided by the abutment 51 serves to protect againstforcing the oven door open and the control insures that access to theoven interior cannot be obtained without following the sequentialcontrol operation insuring that the switch contacts are in openposition. The principal of the invention has been illustrated andexplained herein with respect to what is presently considered torepresent its best embodiments.

Iclaim:

1. A switch assembly, adapted for use with microwave ovens, whichcoordinates the position of an oven door with the closed and openposition of a switching element, said assembly including a housing, apair of stationary contacts mounted within said housing and a moveablecontact member adapted to engage and electrically bridge said stationarycontacts when moved to a first position and to disengage said stationarycontacts when moved to a second position, a pair of spaced plungermembers mounted for movement within said housing and having portionsextending externally of the housing, a plunger-bridging member extendingbetween said plungers and pivotally attached thereto, said bridgingmember carrying said moveable contact member intermediate its ends,whereby when said extending portions of the plungers are successivelydepressed said moveable contact member is incrementally moved from itssaid second position to an intermediate position then to its said firstposition to bridge said stationary contacts.

2. A switch assembly as claimed in claim 1 in which one of saidextending plunger portions is adapted to be engaged and therebydepressed by an oven door as it is closed and the extending portion ofthe other plunger is adapted to be manually depressed.

3. A switch assembly as claimed in claim 2 having resilient means urgingboth of said plungers out of depressed position, and further including aretaining member supported for movement within said housing and havingspaced surfaces engaging said plunger members, the retaining membersurface engaging said ."lllllllllllllltll lllttll l er in positlon w ensaid retaining member is in a first position, the distance between saidplunger engaging surfaces being such that said retaining member canoccupy its said first position only when said door engaged plungerportion is depressed.

4. A switch assembly as claimed in claim 3 having an additional manuallyactuated plunger member mounted adjacent to said manually depressableplunger and having a surface engageable with said retaining member whensaid additional plunger member is manually actuated to move saidretaining member out of its said first position independently of theposition of said oven door, and interlock means between said manuallydepressable plunger and said additional plunger to assure that bothcannot be simultaneously actuated.

5. A switch assembly as claimed in claim 3 having a solenoid mountedadjacent said retaining member, a member moved by energization of saidsolenoid and engaging said retaining member to move it out of its saidfirst position thereby releasing said manually depressable plunger formits depressed position.

6. A switch assembly as claimed in claim 3 in which said door engagedplunger is supported for controlled pivotal motion, said door engagedplunger being provided with a door-latching abutment adapted to retainthe oven door in closed position while said plunger is at one extreme ofits said pivotal motion and to release the oven door when at the otherpivotal motion extreme, said retaining member preventing movement ofsaid door engaged plunger to said other pivotal motion extreme when saidretaining member is in its said first position.

7. A switch assembly as claimed in claim 6 in which a locking abutmentis carried by said housing, and said retaining member is placed inengagement with said locking abutment when both said door engagedplunger and said manually depressable plunger are in depressed position,engagement of said retaining member with said locking abutment providinga positive lock to prevent release of the oven door by said doorlatching abutment until said retaining member is moved out of its saidfirst position.

1. A switch assembly, adapted for use with microwave ovens, whichcoordinates the position of an oven door with the closed and openposition of a switching element, said assembly including a housing, apair of stationary contacts mounted within said housing and a moveablecontact member adapted to engage and electrically bridge said stationarycontacts when moved to a first position and to disengage said stationarycontacts when moved to a second position, a pair of spaced plungermembers mounted for movement within said housing and having portionsextending externally of the housing, a plunger-bridging member extendingbetween said plungers and pivotally attached thereto, said bridgingmember carrying said moveable contact member intermediate its ends,whereby when said extending portions of the plungers are successivelydepressed said moveable contact member is incrementally moved from itssaid second position to an intermediate position then to its said firstposition to bridge said stationary contacts.
 2. A switch assembly asclaimed in claim 1 in which one of said extending plunger portions isadapted to be engaged and therEby depressed by an oven door as it isclosed and the extending portion of the other plunger is adapted to bemanually depressed.
 3. A switch assembly as claimed in claim 2 havingresilient means urging both of said plungers out of depressed position,and further including a retaining member supported for movement withinsaid housing and having spaced surfaces engaging said plunger members,the retaining member surface engaging said manually actuated plungermember being adapted to retain said plunger member in depressed positionwhen said retaining member is in a first position, the distance betweensaid plunger engaging surfaces being such that said retaining member canoccupy its said first position only when said door engaged plungerportion is depressed.
 4. A switch assembly as claimed in claim 3 havingan additional manually actuated plunger member mounted adjacent to saidmanually depressable plunger and having a surface engageable with saidretaining member when said additional plunger member is manuallyactuated to move said retaining member out of its said first positionindependently of the position of said oven door, and interlock meansbetween said manually depressable plunger and said additional plunger toassure that both cannot be simultaneously actuated.
 5. A switch assemblyas claimed in claim 3 having a solenoid mounted adjacent said retainingmember, a member moved by energization of said solenoid and engagingsaid retaining member to move it out of its said first position therebyreleasing said manually depressable plunger form its depressed position.6. A switch assembly as claimed in claim 3 in which said door engagedplunger is supported for controlled pivotal motion, said door engagedplunger being provided with a door-latching abutment adapted to retainthe oven door in closed position while said plunger is at one extreme ofits said pivotal motion and to release the oven door when at the otherpivotal motion extreme, said retaining member preventing movement ofsaid door engaged plunger to said other pivotal motion extreme when saidretaining member is in its said first position.
 7. A switch assembly asclaimed in claim 6 in which a locking abutment is carried by saidhousing, and said retaining member is placed in engagement with saidlocking abutment when both said door engaged plunger and said manuallydepressable plunger are in depressed position, engagement of saidretaining member with said locking abutment providing a positive lock toprevent release of the oven door by said door latching abutment untilsaid retaining member is moved out of its said first position.